Hi Judy, I was born and raised in Sturtevant in the 40's and 50's and have been back every few years. I don't remember any MIELNECZEK/MIELNECZAK living in the area. Could it be that they changed the name, Americanized it?
For a good book on the history of Parkersville/Western Union Junction/Corliss/Sturtevant contact the Village Clerk in Sturtevant, WI 53177. It was published about 6 years ago and contains the history and many pictures, cost about $20 or so if I remember.